<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        
    </style>
</head>
<body>
    
</body>
<script>

    var a = 10;
    console.log(a); //10

    var b;
    console.log(b); //undefined

    var c = a;
    console.log(c); //10

    var d = "true";
    console.log( '====='+ typeof d); //string

    var q, w="hello", e, r=30;

    console.log(q); //undefiend 
    console.log(w); //hello
    console.log(e);  //undefiend
    console.log(r);   //30
    
</script>
</html>